Radiographic image processing apparatus

Abstract

The invention provides an apparatus for processing digital image data of pixels which are obtained by radiographing an image area including a subject so as to generate image signals and by converting the image signals into digital image data, each of the digital image data representing a density level corresponding to an amount of radioactive ray transmitted through each portion of the image area. The apparatus comprises a circuit for analyzing the digital image data of pixels; and a circuit for determining a desired portion of said image area on the basis of the analyzing result and for further determining an image processing condition for the image area on the basis of digital image data of the desired portion.

What is claimed is: 
     
       1. An apparatus for processing digital image data of pixels which are obtained by radiographing an image area including a subject so as to generate image signals, said image signals being converted into digital image data of pixels, each said digital image data of pixels representing a density level corresponding to an amount of radioactive rays transmitted through a respective portion of said radiographed image area, and each pixel having a position data representing the position of the respective pixel on said image area, said apparatus comprising: means for determining a threshold value on the basis of digital image data of said subject;   means for binarizing each said digital image data of pixels of said image area by comparison with said threshold value so that each pixels is represented by a binary code;   means for classifying each pixel in accordance with its binary code and its position data, and for dividing said image area into plural sub-image areas so that all pixels adjoining each other in the same sub-image area have the same binary code;   means for comparing said digital image data and the position data of each of said plural sub-image areas with a predetermined condition to produce a comparison result, and for selecting a desired sub-image area from said plural sub-image areas responsive to the comparison result; and   means for determining an image processing condition for said digital image data of said image area on the basis of said digital image data of said desired sub-image area.   
     
     
       2. The apparatus of claim 1, wherein said threshold value-determining means comprises means for determining said threshold value on the basis of picked-up digital image data in a predetermined area at a center portion of said image area. 
     
     
       3. The apparatus of claim 2, wherein said picked-up digital image data indicates a maximum density level in said predetermined area. 
     
     
       4. The apparatus of claim 2, wherein said picked-up digital image indicates a minimum density level in said predetermined area. 
     
     
       5. The apparatus of claim 1, wherein said threshold value-determining means includes means for producing a histogram of said digital image data and for determining said threshold value on the basis of a value in a portion of said histogram corresponding to the subject. 
     
     
       6. The apparatus of claim 5, wherein said value on the basis of which said threshold value-determining means determines said threshold value indicates the maximum density level in said portion of said histogram corresponding to the subject. 
     
     
       7. The apparatus of claim 5, wherein said value on the basis of which said threshold value-determining means determines said threshold value indicates the minimum density level in said portion of said histogram corresponding to the subject. 
     
     
       8. The apparatus of claim 1, wherein said threshold value-determining means includes means for picking up said digital image data along a line across said image area and for determining said threshold value on the basis of a value in a portion corresponding to the subject on said line. 
     
     
       9. The apparatus of claim 8, wherein said value on the basis of which said value-determining means determines said threshold value indicates the maximum density level in said portion corresponding to the subject on said line. 
     
     
       10. The apparatus of claim 8, wherein said value on the basis of which said value-determining means determines said threshold value indicates the minimum density level in said portion corresponding to the subject on said line. 
     
     
       11. The apparatus of claim 1, wherein, when said selecting means does not select said desired sub-image area in consideration of the comparison result, said threshold value-determining means changes said threshold value to another threshold value and said binarizing means binarizes each of said digital image data of pixels with said another threshold value. 
     
     
       12. The apparatus of claim 1, wherein, when said image area includes a non-subject portion, said threshold value is lower than a density level of said non-subject portion of said image area. 
     
     
       13. The apparatus of claim 1, wherein said threshold value is higher than a density level of a high density portion of said image area. 
     
     
       14. A method of processing digital image data of pixels which are obtained by radiographing an image area including a subject so as to generate image signals, said image signals being converted into digital image data of pixels, each said digital image data of pixels representing a density level corresponding to an amount of radioactive rays transmitted through a respective portion of said radiographed image area, and each pixel having a position data representing the position of the respective pixel on said image area, said method comprising: determining a threshold value on the basis of digital image data of said subject;   binarizing each said digital image data of pixels of said image area by comparison with said threshold value so that each pixels is represented by one of a binary code;   classifying each pixel in accordance with its binary code and its position data;   dividing said image area into plural sub-image areas so that all pixels adjoining each other in the same sub-image area have the same binary code;   comparing said digital image data and the position data of each of said plural sub-image areas with a predetermined condition, and producing a comparison result;   selecting a desired sub-image area from said plural sub-image areas responsive to the comparison result; and   determining an image processing condition for said digital image data of said image area on the basis of said digital image data of said desired sub-image area.   
     
     
       15. The method of claim 14, wherein, when in said step of selecting said desired sub-image area, a desired area cannot be selected, said threshold value is changed to another threshold value and each of said digital image data of pixels is binarized with said another threshold value. 
     
     
       16. The method of claim 14, wherein said image area is divided into a plurality of sub-image areas, each sub-image area having the same binary code. 
     
     
       17. The method of claim 16, wherein said desired image area is selected in accordance with a position of each of the plurality of sub-image areas having the same binary code. 
     
     
       18. The method of claim 14, wherein said subject is a human body. 
     
     
       19. The method of claim 18, wherein said desired image area is a lung field.